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D.M. Little, K.R. Thulborn, J.P. Szlyk; Cortical Networks Underlying Saccadic and Smooth Pursuit Eye Movements in AMD . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5874.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the integrity of the cortical networks, using functional Magnetic Resonance Imaging (fMRI), that underlie saccadic and smooth pursuit eye movements in patients with age–related macular degeneration (AMD).
Five patients with AMD (range 55 – 83 years of age, M=69.8), recruited from a reading rehabilitation program, completed two eye movement tasks while fMRI data were acquired. The patients’ visual acuities ranged from 20/76 to 20/360 in their better eye. Eye movement was monitored during scanning to insure task performance. Patients first completed a visually guided saccade (VGS) task which required alternating periods of central fixation with 3° eye movements along the horizontal plane. Patients then completed a smooth pursuit (SMP) task which required patients to follow a dot along the horizontal plane (alternating with fixation). FMRI data were acquired on a 3.0–Tesla whole body scanner (GEMS, Waukesha, WI) using serial gradient echo, echo–planar imaging. Following fMRI data acquisition, a high–resolution anatomical scan was completed for all subjects.
The networks utilized in both VGS and SMP in controls implicated regions in the frontal eye fields (FEF), supplementary eye fields (SEF), portions of both inferior and superior parietal lobules (IPL, SPL), and MT/V5. FMRI data for AMD were highly variable and were marked by a decrease or absence of activity in SEF and FEF and increased activity in SPL. In comparison, the AMD patients showed networks that were similar to controls during performance of SMP.
The VGS task is traditionally thought to reflect reflexive eye movements driven by the onset of a target in the visual field. We interpret the deviant patterns of activation during the VGS in AMD to reflect the patients’ difficulties in visual search and identification of targets in their visual field. These findings may have implications for the development of rehabilitation programs aimed at AMD.
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